U.S. patent number 7,365,768 [Application Number 09/483,883] was granted by the patent office on 2008-04-29 for endoscope apparatus and function adjusting circuit for endoscope.
This patent grant is currently assigned to Olympus Corporation. Invention is credited to Masanao Murata, Mitsunobu Ono.
United States Patent |
7,365,768 |
Ono , et al. |
April 29, 2008 |
Endoscope apparatus and function adjusting circuit for
endoscope
Abstract
An endoscope includes an insert section, a CCD is mounted at the
end of the insert section, and a CCU for producing a video signal
is arranged in a control unit connected to a proximal end of the
insert unit. The CCU includes a general-purpose DSP board having
the function of producing a standard video signal, and a function
adjustment/expansion circuit board for correcting a signal delay
due to the length of a signal line connected to the CCD. The DSP
boards and the function adjustment/expansion circuit boards,
respectively remaining the same in circuit arrangement, are used
for a plurality of types of endoscopes having insert sections
having different insertion lengths.
Inventors: |
Ono; Mitsunobu (Tokyo,
JP), Murata; Masanao (Tokorozawa, JP) |
Assignee: |
Olympus Corporation
(JP)
|
Family
ID: |
11830091 |
Appl.
No.: |
09/483,883 |
Filed: |
January 18, 2000 |
Foreign Application Priority Data
|
|
|
|
|
Jan 21, 1999 [JP] |
|
|
11-013328 |
|
Current U.S.
Class: |
348/76;
348/E5.042; 348/72; 600/112; 600/114; 600/109; 600/101; 348/77;
600/130; 348/65; 348/E9.052 |
Current CPC
Class: |
H04N
9/735 (20130101); H04N 7/183 (20130101); A61B
1/042 (20130101); G02B 23/2476 (20130101); H04N
5/23206 (20130101); H04N 2005/2255 (20130101) |
Current International
Class: |
H04N
7/18 (20060101) |
Field of
Search: |
;348/76,445,220.1,335,458,72,69,45,77,74,68,65,70,376,521,518
;600/152,117,101,139,114,109,112,130 ;388/838 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: An; Shawn S.
Attorney, Agent or Firm: Ostrolenk, Faber, Gerb &
Soffen, LLP
Claims
What is claimed is:
1. An endoscope, comprising: an elongated insert section; a
solid-state image pickup device for picking up an image, the
solid-state image pickup device being provided to an end portion of
the insert section; a general-purpose video signal processing
circuit including a drive signal generating section for generating
a drive signal for driving the solid-state image pickup device, and
a video signal processing section for producing a standard video
signal in response to an output signal outputted from the
solid-state image pickup device, wherein the general-purpose video
signal processing circuit is mounted on a first common board along
with a first microcomputer that performs operation setting of the
general-purpose video signal processing circuit; an adjusting
circuit including a timing adjusting section for performing timing
adjustment of the drive signal by receiving and thereafter delaying
the drive signal generated by the drive signal generating section
in accordance with a delay time and transmitting the delayed drive
signal to the solid-state image pickup device such that the output
signal to be inputted to the general-purpose video signal
processing circuit has a correct timing, and a signal processing
adjusting section for adjusting signal processing with respect to
the video signal processing section, wherein the adjusting circuit
is mounted on a second common board along with a second
microcomputer for controlling the adjusting circuit, and wherein
the first microcomputer is connected to the second microcomputer
through an interface; and a video signal output connector for
outputting the standard video signal outputted from the
general-purpose video signal processing circuit to an external
display unit.
2. The endoscope according to claim 1, wherein the general-purpose
video signal processing circuit and the adjusting circuit are
disposed in an operational section arranged at a proximal end of
the insert section.
3. The endoscope according to claim 1, wherein the adjusting
circuit is mounted on a second common board along with a second
microcomputer for controlling the adjusting circuit.
4. The endoscope according to claim 1, wherein the timing adjusting
section comprises a delay amount adjusting circuit which receives
the drive signal generated by the drive signal generating section
and a signal corresponding to an amount of a delay time and
thereafter delays the received drive signal and transmits the
delayed drive signal to the solid-state image pickup device.
5. The endoscope according to claim 4, wherein the amount of delay
time that the drive signal is delayed by the delay amount adjusting
circuit corrects a time delay for the drive signal outputted by the
drive signal generating section to be applied to the solid-state
image pickup device and a time delay for the output signal
outputted from the solid-state image pickup device to be inputted
to the video signal processing section, to input the output signal
to the video signal processing section at a predetermined
timing.
6. The endoscope according to claim 1, wherein the general-purpose
video signal processing circuit comprises a digital signal
processor.
7. The endoscope according to claim 1, wherein the end portion
includes a wave shaping circuit for performing wave shaping of the
drive signal timing-adjusted by the timing section and applying the
wave-shaped drive signal to the solid-state image pickup
device.
8. The endoscope according to claim 1, further comprising a light
guide for transmitting illumination light, an end portion of the
light guide being detachably connected to an external light source
device.
9. The endoscope according to claim 1, wherein the signal
processing adjusting section comprises a pixel-number signal
adjusting section for adjusting signal processing by the video
signal processing section compatibly with different numbers of
pixels of the solid-state image pickup device.
10. The endoscope according to claim 1, further comprising an
electrical bending driving section for controlling bending of a
bending portion provided to the insert section.
11. The endoscope according to claim 1, further comprising an
external remote control circuit detachably connected to the
endoscope.
12. The endoscope according to claim 1, wherein the video signal
output connector outputs a plurality of standard video signals of
different types.
13. The endoscope according to claim 1, further comprising a
connecting terminal for a remote control provided outside the
endoscope for remote-controlling the general purpose video signal
processing circuit.
14. An endoscope comprising: an elongated insert section; a solid
state image pick up device for picking up an image, and the
solid-state image pickup device being provided to an end portion of
the insert section; a general-purpose video processing circuit
including a drive signal generating section for generating a drive
signal for driving the solid-state image pickup device, and a video
signal processing section for producing a standard video signal in
response to an output signal outputted from the solid-state image
pickup device; an adjusting circuit including a timing adjusting
section for performing timing adjustment of the drive signal
generated by the drive signal generating section such that the
output signal to be inputted to the general-purpose video
processing circuit has a correct timing, and a signal processing
adjusting section for adjusting signal processing with respect to
the video signal processing section; and a video signal output
connector for outputting the standard video signal outputted from
the general-purpose video signal processing circuit to an external
display unit; wherein the general-purpose video signal processing
circuit is mounted on a first common board along with a first
microcomputer that performs operation setting of the
general-purpose video signal processing circuit, the adjusting
circuit is mounted on a second common board alone with a second
microcomputer for controlling the adjusting circuit, and the first
microcomputer is connected to the second microcomputer through an
interface.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an endoscope apparatus having a
general-purpose video signal processing circuit which is provided
with an adjustment function or expanded function, such as signal
processing, adapted for use in a solid-state image pickup device
built in an endoscope and to an endoscopic function adjusting
circuit.
2. Description of the Related Art
As disclosed in Japanese Unexamined Patent Publication No.
63-283277, an endoscope apparatus having an image pickup device
tends to become complex in the structure of the circuit therein
because of the necessity of correcting a signal delay due to a
cable running through the insert section thereof and correcting the
waveform of a CCD drive pulse.
For this reason, in the conventional art, all signal processing
circuits for driving an image pickup device and processing an
output signal of the image pickup device are built in an endoscope
side. The endoscope having the built-in image pickup device needs
signal processing circuits including a CDS circuit, an AGC circuit,
an A/D converter, an encoder, etc.
In the conventional art, each of the signal processing circuits
built in the endoscope needs to be developed as a circuit dedicated
to the endoscope. Since each circuit needs to be developed and
prepared each time the need arises, the circuit lacks versatility.
If many models of endoscopes are manufactured in a production
system, of which a large-inventory and small-production quantity
method is currently required, circuits need to be newly developed
and prepared in accordance with the types of endoscopes, and
development costs involved increase.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an endoscope
apparatus having a signal processing circuit that is low-cost and
compatible with a number of models of endoscopes, and to a function
adjusting circuit for the endoscopes.
It is another object of the present invention to provide an
endoscope apparatus which is realized at a low cost by adding an
endoscopic function adjusting circuit specific to a common
general-purpose signal processing circuit to be compatible with
many models of endoscopes having insert sections having insertion
lengths, and an endoscopic function adjusting circuit for the
endoscope.
An endoscope apparatus of the present invention includes a
solid-state image pickup device mounted at the end of an insert
section of an endoscope and a signal processing circuit, arranged
in the endoscope, for driving the solid-state image pickup device
and for producing a standard video signal in response to an output
signal from the solid-state image pickup device,
wherein the signal processing circuit comprises a general-purpose
video signal processing circuit having a drive signal generation
function for driving the solid-state image pickup device and a
signal processing function for outputting the standard video signal
by processing the output signal from the solid-state image pickup
device, and
an endoscopic function adjusting circuit comprising a function
modifying circuit, connected to the general-purpose video
processing circuit, for modifying at least one of the drive signal
processing function and the signal processing function executed by
the general-purpose video signal processing circuit to perform
signal processing compatible with the solid-state image pickup
device mounted at the end of the insert section.
An endoscopic function adjusting circuit of the present invention,
connected to a general-purpose video processing circuit, for
driving a solid-state image pickup device built in an endoscope,
and for outputting a standard video signal by processing an output
signal of the solid-state image pickup device,
includes a function modifying circuit for modifying at least one of
the drive signal processing function and the signal processing
function executed by the general-purpose video processing signal in
accordance with the endoscope having the solid-state image pickup
device therein.
Other features and advantages of the present invention will become
apparent from the following description.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 through FIG. 7 show a first embodiment of the present
invention, wherein FIG. 1 is a block diagram showing the general
construction of an endoscope system of the present invention,
FIG. 2 is a block diagram showing the construction of an endoscope
apparatus,
FIG. 3 is a block showing the internal construction of a DSP,
FIG. 4 is a circuit diagram showing the construction of a DL delay
circuit,
FIG. 5 is a diagram explaining the operation of the circuit shown
in FIG. 4,
FIG. 6 is a circuit diagram showing the construction of an HIC
circuit, and
FIG. 7 is a diagram explaining the operation of the circuit shown
in FIG. 6, and
FIG. 8 and FIG. 9 show a second embodiment of the present
invention, wherein FIG. 8 is a block diagram showing the general
construction of an endoscope system, and
FIG. 9 is a block diagram showing the construction of an endoscope
apparatus, and
FIG. 10 and FIG. 11 show a third embodiment of the present
invention, wherein FIG. 10 is a block diagram showing the
construction of an endoscope apparatus, and
FIG. 11 is a block diagram showing the construction of an
electrical system of an endoscope apparatus, and
FIG. 12 and FIG. 13 show a fourth embodiment of the present
invention, wherein FIG. 12 is a block diagram showing the general
construction of an endoscope system, and
FIG. 13 is a block diagram showing the construction of an
electrical system of an endoscope apparatus, and
FIG. 14 is a block diagram showing the construction of an
electrical system of an endoscope apparatus of a fifth embodiment
of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The embodiments of the present invention are now discussed,
referring to the drawings.
First Embodiment
FIG. 1 through FIG. 7 show a first embodiment of the present
invention, wherein FIG. 1 is a block diagram showing the general
construction of an endoscope system of the first embodiment of the
present invention, FIG. 2 is a block diagram showing the
construction of an endoscope apparatus, FIG. 3 is a block showing
the internal construction of a DSP, FIG. 4 is a circuit diagram
showing the construction of a DL delay circuit, FIG. 5 is a diagram
explaining the operation of the circuit shown in FIG. 4,
FIG. 6 is a circuit diagram showing the construction of a hybrid IC
circuit, and FIG. 7 is a diagram explaining the operation of the
circuit shown in FIG. 6.
Referring to FIG. 1, an endoscope system 1, incorporating the first
embodiment of the present invention, includes a plurality of
endoscopes 2A, 2B, and 2C, each containing its own image pickup
means, a light source device 3 for supplying illumination light to
an endoscope 2I (I=A, B, or C) connected thereto, a liquid-crystal
display monitor 4 for displaying an endoscopic image picked up, an
operational remote control unit (simply referred to as remote
control) 5, detachably connected to an external remote control
terminal of the endoscope 2I, for performing a zooming operation,
and a personal computer (simply referred to as a computer) 6,
detachably connected to a serial terminal of the endoscope 2I, for
exchanging data.
The endoscope 2I includes an elongated insert section 11I being
different in length, a control section 12 arranged at the proximal
end of the insert section 11I, and a universal cable 13 that is
extended from one side of the control section 12, and the incident
end of a light guide 15 extending from a connector 14 on the other
end of the universal cable 13 is detachably connected to the light
source device 3.
A video terminal 16, an external remote terminal 17, and a serial
terminal 18 arranged on the connector 14 are respectively connected
to the liquid-crystal display monitor 4, the remote control 5, and
the computer 6 via respective interconnect cables.
A lamp 21, such as a halogen lamp, is arranged in the light source
device 3, and white light emitted from the lamp 21 is condensed by
a condenser lens 22 and is then directed to the end face of the
light guide 15.
Illumination light, transmitted through the light guide 15 running
through the endoscope 2I, is forwardly projected through the end
face of the light guide fixed to an illumination window of an end
portion 24 of the insert section 11I to illuminate an object, such
as a lesion of a subject.
The end portion 24 has an observation window (an image pickup
window) next to the illumination window, and an objective lens 25
is mounted on the observation window, and a charge-coupled device
(simply referred to as CCD) 26 is arranged at a focus position of
the objective lens 25, and photoelectrically converts an optical
image. The endoscope 2I in this embodiment is thus an electronic
endoscope having a CCD 26 at the end portion 24 of the insert
section 11I.
A color separation filter, such as an unshown mosaic filter, is
arranged on the imaging surface (a photosensitive surface) of the
CCD 26, performing color separation on a per pixel basis.
In this embodiment, a hybrid integrated circuit (simply referred to
as HIC) 27 having a wave shaping function is arranged in the end
portion 24, namely, in the vicinity of the CCD 26, and wave-shapes
a CCD drive signal, transmitted through a signal line 28I, for
driving the CCD 26 before applying it to the CCD 26.
The CCD 26 is connected, via the signal line 28I, to a camera
control unit (simply referred to as CCU) 29, which is a video
signal processing circuit arranged in the control section 12.
In this embodiment, the CCU 29 includes a DSP board 30 having a
digital signal processor (simply referred to as DSP) thereon as a
general-purpose board with a function for generating a standard
video signal, and a function adjustment/expansion circuit board
31I, connected to the DSP board 30, having function adjusting
(function modification) means or function expansion means
compatible with functions specific to the endoscope.
Since the DSP board 30 has the function of generating the standard
video signal, a monitor displays an image picked up by the CCD 26
if the DSP board 30 (CCD drive circuit) is connected to the CCD 26
directly (or via a short cable) with the video signal output
terminal thereof connected to the monitor.
Specifically, the DSP board 30 has the CCD drive function to
generate a CCD drive signal to the CCD 26 and the video signal
processing function to generate the standard video signal by
processing the CCD drive signal output by the CCD 26 in response to
the CCD drive signal. The function adjustment/expansion circuit
board 31 has the function modification means or the function
expansion means corresponding to functions (for example, a function
of canceling the effect of a signal delay) that are required of the
endoscope 2I which has insert section 11I different in length from
type to type (therefore, having a signal delay amount dependent on
the length of the signal line 28I between the CCD 26 and the CCU
29). In this embodiment, the DSP board 30, with the function
adjustment/expansion circuit board 31 connected thereto, works with
the endoscope 2I having a different insertion length (cable length)
(in other words, performing signal processing compatible with the
CCD 26 that is arranged on the end portion of the insert section in
the endoscope 2I having a different insertion length).
In this embodiment, the function adjustment/expansion circuit board
31 has a different set value for the endoscope 2A (the CCD 26
arranged at the end portion of the insert section 11I when the
insertion length is different) depending on the insertion length
(cable length). Even when the insertion length is different, the
common function adjustment/expansion circuit board 31 is set to
work, thereby reducing costs of the apparatus.
In the present embodiment, the CCU 29 is supplied with power
required for the operation thereof by an unshown power supply
circuit in the light source device 3.
FIG. 2 shows the construction of an electrical system of the
endoscope apparatus having the endoscope 2A, for example. The DSP
board 30 includes a DSP 32 having (a CCD drive function and) a
signal processing function. In the DSP 32, as shown in FIG. 3, a
CCD drive & TG circuit 34 generates a CCD drive signal and a
timing signal (simply referred to as TG) in synchronization with a
timing signal of a system signal generator circuit (simply referred
to as an SSG circuit) 33 in the DSP 32. The CCD drive signal and
the timing signal are fed to a delay line delay circuit (simply
referred to as DL delay circuit) 35, and are adjusted by the DL
delay circuit 35 in timing corresponding to the cable length
(signal line length) in accordance with a delay amount setting
signal coming from a DSP controlling microcomputer (simply referred
to as DSP controlling computer) 36.
The DSP controlling computer 36 is connected to a DIP switch 37,
for instance, and outputs, to the DL delay circuit 35, a
corresponding delay amount setting signal of a plurality of bits in
response to a combination of ON/OFF settings of the DIP switch
37.
The output signal of the DL delay circuit 35 is amplified by a
drive amplifier 38, then applied to a HIC 27 through a drive signal
line 28Aa forming the signal line 28A, wave-shaped by the HIC 27,
and then fed to the CCD 26 arranged in the vicinity of the HIC
27.
In response to the application of the CCD drive signal, the CCD 26
gives a photoelectrically converted CCD output signal, and the CCD
output signal is fed to a preamplifier 39 in the function
adjustment/expansion circuit board 31 for amplification through an
output signal line 28Ab forming the signal line 28A, and is fed to
a correlated double sampling circuit (simply referred to as CDS
circuit) 40 in the DSP board 30, and a signal component is
extracted from the CCD output signal.
As will be discussed later, the CDS circuit 40 extracts the signal
component from a signal portion in response to a sampling pulse at
a correct timing in the same manner as in the case when no signal
delay takes place, because of the signal delay in the CCD drive
signal provided by the DL delay circuit 35.
The output signal of the CDS circuit 40 is converted through an A/D
converter circuit 41 into a digital signal, which is then fed to a
digital optical black clamp circuit (simply referred to as digital
OB clamp circuit) 42 in the DSP 32. A process is performed to set,
to a black level, an output signal level in an OB section in each
of all pixels in the CCD 26, where light is blocked, and then the
signal is fed to a digital gamma circuit 43.
After being subjected to gamma correction through the digital gamma
circuit 43, the output of the CDS circuit 40 is fed to a color
separation/color signal processing circuit 44 for performing color
separation and color signal processing and to a digital low-pass
filter circuit (simply referred to as digital LPF circuit) 45.
The color separation/color signal processing circuit 44 subjects
the above signal to color separation and color signal processing,
resulting in color-difference signals R-Y and B-Y (U and V) as
color signals C, which are then input to a white balance variable
amplifier 46. After being white balance adjusted, the color signals
C are then input, to a digital control and processing unit 47
including a digital input and output controller 47a for controlling
digital input and output, a sampling frequency conversion
controller 47b for controlling sampling frequency conversion, and a
digital ZOOM processor 47c for processing digital zooming.
In this embodiment, the white balance variable amplifier 46
performs white balance adjustment when the lamp 21 in the light
source device 3 is a light source lamp.
After being extracted from the signal input to the digital LPF
circuit 45, a digital luminance signal Y component is fed to a
digital enhancement circuit 48, where horizontal and vertical
enhancements are performed thereon. The resulting luminance signal
Y component is input to a digital white clipping circuit 49, where
the luminance signal is clipped at a white level. The clipped
signal is then fed to the digital control and processing unit
47.
The digital luminance signal Y and the color signals C output by
the digital control and processing unit 47 are fed to a digital
encoder circuit 50. The digital encoder circuit 50 converts these
signals into a digital composite video signal (composite signal)
VBS in which the luminance signal Y, the color signals C and the
synchronization signal are superimposed, and Y/C separate signals
(Y/C component signals) containing the luminance signal Y and the
color signals C. The digital composite video signal VBS and the
digital Y/C separate signals are converted by a D/A converter
circuit 51 into an analog composite video signal VBS and analog Y/C
separate signals, which are then respectively output from a
composite video signal output terminal 54 and a Y/C separate video
signal output terminal (S terminal) 55 via buffer amplifiers 52 and
53 as shown in FIG. 2.
The composite video signal VBS output from the buffer amplifier 52
is input to an RGB decoder 56 in the function adjustment/expansion
circuit board 31 and is converted into an RGB signal for driving
the liquid-crystal display monitor 4. An object is thus displayed
in color on the liquid-crystal display monitor 4.
The digital control and processing unit 47 outputs the digital
luminance signal Y and the digital color signals (color-difference
signals R-Y and B-Y, or U and V) at a ratio of Y:U:V=4:2:2 (or
Y:U:V=4:2:0) while controlling and processing the digital luminance
signal Y and the digital color signals C input thereto at a ratio
of Y:U:V=4:2:2 (or Y:U:V=4:2:0).
The DSP board 30 includes the DSP 32 and a microcomputer 58 for
bilaterally exchanging information through an internal
microcomputer interface 57. The microcomputer 58 is connected to
the DSP controlling computer 36 in the function circuit board 31
through a serial interface, for instance, and changes or sets an
operation mode of the DSP 32 through the DSP controlling computer
36.
The system SSG circuit 33 in the DSP 32 is supplied with a
reference clock, from a crystal oscillator circuit 59 in the DSP
board 30, used to read data from pixels of the CCD 26. In
synchronization with the reference clock, the system SSG circuit 33
generates and outputs a variety of timing signals including a
synchronization signal for the video system. Receiving an external
synchronization signal at the external synchronization input
terminal, the system SSG circuit 33 generates a variety of timing
signals in synchronization with the external synchronization
signal.
In this embodiment, the DSP controlling computer 36 is connected to
the HIC 27 through a signal line 28Ac so that the DSP controlling
computer 36 changes the wave shaping operation mode by the HIC
27.
FIG. 4 shows the construction of the DL delay circuit 35. For
instance, the DL delay circuit 35 includes a delay unit 62 having a
number of connected delay lines or delay elements (labeled D in
FIG. 4) 61 for a constant time delay, and a multiplexer (or a
selection switch) 63 for selecting and setting the amount of delay
by selecting a junction j (j=a, b, c, d, e, . . . ) connected to
the delay lines 61. The selection of the junction j by the
multiplexer 63 is determined in response to the delay amount
setting signal from the DSP controlling computer 36.
The DL delay circuit 35 corrects the time delay in the CCD drive
signal and the CCD output signal due to the insertion length or the
cable length.
For instance, in the endoscope 2A having the longest cable length,
the endoscope 2B having the medium cable length, and the endoscope
2C having the shortest cable length, the delay time is set for a
horizontal transfer signal .phi.H of the CCD drive signal as shown
in FIG. 5(B), FIG. 5(C), and FIG. 5(D) so that the phase thereof is
advanced by the delay time due to the cable length from a (next)
horizontal transfer signal .phi.H when no delay is introduced as
shown in FIG. 5(A) (meaning that the CCD 26 is installed in the CCU
29) and the input timings of the CCD output signal into the CDS
circuit 40 are aligned without dependence on the cable length.
The CDS circuit 40 extracts the signal component at the CDS
sampling pulse (at the timing of the horizontal transfer signal
.phi.H without considering the cable length as shown in FIG. 5(A)),
thereby extracting the signal of the CCD output signal at the
timing when the signal is input (even when the cable length is
changed).
For simplification, as shown in FIG. 5, the signal delay amount is
shorter than a duration corresponding to a single pixel even in the
endoscope 2A having the longest cable length. When the signal delay
amount is longer than the duration corresponding to a single pixel,
the timing is synchronized with the horizontal transfer signal
.phi.H with no delay introduced, after a duration corresponding to
two pixels or three pixels.
Referring to FIG. 5, the horizontal transfer signal .phi.H is
shown. Besides this, a reset gate pulse .phi.R and a vertical
transfer pulse .phi.V are similarly time-delayed through the DL
delay circuit 35.
In this way, the CDS circuit 40 and the like are aligned with the
timing of the CCD output signal with no delay, thereby extracting
the signal component of the CCD output signal.
A buffer or the like may be used for the delay line (delay element)
61, and the delay amount is changed by the number of stages of the
buffer.
Since the wave of the CCD drive signal applied to the CCD 26 is
subject to change depending on the cable length, the HIC 27 for
wave shaping is arranged in the vicinity of the CCD 26 in this
embodiment to shape the wave of the CCD drive signal.
FIG. 6 shows the construction of the HIC 27 as a wave shaping
circuit.
The HIC 27 includes comparators 65, 66, and 67 for performing wave
shaping in response to input two-phase horizontal transfer signals
.phi.H1 and .phi.H2, and reset gate signal .phi.RG of the CCD drive
signal, and a voltage regulator 68 for determining the output
levels of the comparators 65, 66, and 67.
The horizontal transfer signals .phi.H1 and .phi.H2 and the reset
gate signal .sctn.RG are fed to respective inverting input
terminals of the comparators 65, 66, and 67, and a common
comparator voltage signal Vr is fed to non-inverting input
terminals of the comparators 65, 66, and 67. The comparator voltage
signal Vr is applied from the DSP controlling computer 36 through
the signal line 28Ac.
The voltage regulator 68 is supplied with a voltage mode switching
signal Vc from the DSP controlling computer 36 through the signal
line 28Ac. The voltage mode switching signal Vc at an "L" level or
an "H" level in accordance with the type of the CCD 26 is applied
to the voltage regulator 68. The voltage regulator 68 feeds a power
source voltage at a corresponding voltage level (5 V or 8 V, for
instance) to the power supply terminals of the comparators 65, 66,
and 67. The comparators 65, 66, and 67 supply the CCD 26 with the
CCD drive signals at the required voltage level.
FIG. 7 shows the operation of the HIC 27 shown in FIG. 6. Referring
to FIG. 7(A), the reset gate signal .phi.RG is input to the
comparator 65, as an input signal (for the comparator) having the
wave thereof deformed through the cable, and is compared with the
comparator voltage signal Vr. As a result, a wave-shaped output
signal .phi.RG shown in FIG. 7(B) is output.
FIG. 7 shows the reset gate signal .phi.RG, and the horizontal
transfer signals .phi.H1 and .phi.H2 are also similarly shaped.
By variably setting the level of the comparator voltage signal Vr
in this embodiment, the CCD 26 is supplied with the reset gate
signal .phi.RG having a proper pulse width T unaffected by sagging
thereof. For instance, at a level represented by a two-dot chain
line as shown in FIG. 7(A), supplying the CCD 26 with an
appropriate reset gate signal .phi.RG is difficult under the effect
of the sagging. In this embodiment, even if the wave of the CCD
drive signal is deformed depending on the cable length, the
comparator voltage signal Vr is set according to the wave
deformation due to the cable length. The CCD 26 is thus constantly
supplied with the CCD drive signal having an appropriate pulse
width T.
When the CDS circuit 40 extracts the signal component from the CCD
output signal, the extraction timing is prevented from being
slipped.
In accordance with the present embodiment, the CCD 26 is arranged
on the end portion 24 of the insert section 11I of the endoscope 2I
having a different insertion length, and when the cable length to
the CCU 29 in the endoscope 2I is different, the signal processing
appropriate to each CCD 26 is carried out.
In this case, the CCU 29 includes the common DSP board 30 and the
function adjustment/expansion circuit board 31 having a different
delay set in the drive signal in accordance with the insertion
length (cable length) so that the CCU 29 is compatible with each
CCD even with the insertion length different. With a low cost
involved, the CCU 29 thus works with the endoscope 2I having a
different insertion length.
Second Embodiment
A second embodiment of the present invention is now discussed,
referring to FIG. 8 and FIG. 9. FIG. 8 shows an endoscope system 1'
of the second embodiment. The endoscope system 1 employs one of a
light source device 3A of a metal halide lamp 21A and a light
source device 3B of a xenon lamp 21B, instead of the light source 3
in the endoscope system 1 shown in FIG. 1.
Since the metal halide lamp 21A and the xenon lamp 21B are
different from each other in color temperature (the wavelength
distribution of emitted light), white balance adjustment is needed
at different settings. For this reason, the CCU 29 in the endoscope
2I is provided with means for setting white balance corresponding
to the light source device 3A or 3B depending on whether the light
source 3A or 3B is in use. In this embodiment, the CCU 29 includes
the DSP board 30 identical to the one in the first embodiment, and
a function adjustment/expansion circuit board 31' including white
balance setting means respectively corresponding to the light
sources 3A and 3B, instead of the function adjustment/expansion
circuit board 31 in the first embodiment. The light sources 3A and
3B respectively include identification signal generator circuits
70A and 70B for generating unique identification information (ID
information).
When mounted, the signal from the identification information signal
generator circuit 70A or 70B respectively arranged in the light
source device 3A or 3B is input to the DSP controlling computer 36
in the function adjustment/expansion circuit board 31' as shown in
FIG. 9.
FIG. 9 shows the construction of an electrical system of the
endoscope 2A to which the light source device 3A is connected. When
the light source device 3A is connected to the endoscope 2A, the
identification signal generator circuit 70A, including a resistor
Ra (a resistor Rb in the light source device 3B), for instance,
provides, to the DSP controlling computer 36, the identification
information indicating the type of the light source lamp (the metal
halide lamp 21A here) at a voltage level determined by dividing the
power source voltage Vcc by a reference resistor R and the resistor
Ra.
The function adjustment/expansion circuit board 31' includes a gain
setting circuit 71 for setting gains for a plurality of color
signals in accordance with the type of the light source lamp. The
output of the gain setting circuit 71 is fed to A/D converters 73
and 74 via a selector 72 to be converted into digital signals,
which are then fed to the DSP controlling computer 36 (the A/D
converters 73 and 74 are dispensed with if the DSP controlling
computer 36 has the A/D conversion function).
Specifically, the gain setting circuit 71 includes gain setting
potentiometers 75r and 76r for setting gains for the color signals
of R and B with the G color signal set as a reference, and gain
setting potentiometers 75b and 76b for setting gains for the color
signals of R and B for setting the white balance in the xenon lamp
21B.
The signal from the gain setting potentiometers 75r and 75b for the
color signal of R and the signal from the gain setting
potentiometers 76r and 76b for the color signal of B are fed to the
A/D converters 73 and 74 via the selector 72 to be converted into
the digital signals, which are then fed to the DSP controlling
computer 36.
The DSP controlling computer 36 generates a selection signal from
the ID information, and selects the R gain and B gain of the light
source corresponding to the ID information through the selector 72.
When the light source device 3A is connected as shown in FIG. 8,
the DSP controlling computer 36 receives the R gain and B gain
(namely, voltage values across the resistors determining the R gain
and B gain) determined by the gain setting potentiometers 75r and
76r for setting the white balance in the wavelength distribution of
the illumination light of the metal halide lamp 21A therein as a
light source.
The DSP controlling computer 36 feeds, via the microcomputer 58 in
the DSP board 31, an R gain controlling signal and B gain
controlling signal to gain control terminals of dual variable
amplifiers 77 and 78 in the white balance variable amplifier 46 in
the DSP 32. The DSP controlling computer 36 thereby sets a white
balance state to match the metal halide lamp 21A.
The DSP controlling computer 36 feeds, via the microcomputer 58, an
auto gain stop signal to an auto white balance circuit 79 in the
DSP 32 to stop the operation of the auto white balance circuit 79.
Although the discussion of the auto white balance circuit 79 is
omitted in conjunction with the first embodiment, the DSP 32 for
performing general-purpose video signal processing is typically
provided with the auto white balance circuit 79. The auto white
balance circuit 79 automatically sets the white balance by
adjusting the R and B gains so that the averages of the color
signals in the signal picked up from light reflected from an object
under the natural light are balanced.
To this end, in this embodiment, the white balance is precisely set
in response to the wavelength distribution of the illumination
light from each lamp, different from that of the natural light.
Referring to FIG. 9, a color separation circuit 44' collectively
represents the blocks designated reference numerals 44-49 shown in
FIG. 3, and a post-process circuit 80 collectively represents the
digital control and processing unit 47 and the digital encoder
circuit 50 shown in FIG. 3. The crystal oscillator circuit 59 shown
in FIG. 2 is represented by OSC 59. The remaining construction,
operation and advantages of the second embodiment is identical to
those of the first embodiment.
In this embodiment, the means for generating the ID information
unique to the light source device 3A or 3B is arranged to set the
white balance in accordance with the light source device 3A or 3B
connected to the endoscope 2I in use. As represented by two-dot
chain lines in FIG. 9, the endoscope 2I may be provided with a
selection switch 81 to be switched in response to the light source
device 3A or 3B, and a selection signal from the selection switch
81 may be used as a command signal (or ID information) to be fed to
the DSP controlling computer 36 to set the white balance in
response to the light source device 3A or 3B.
Besides the advantages of the first embodiment, in accordance with
the present embodiment, an endoscopic examination is carried out in
white balance states suitable to the light sources 3A and 3B which
are different in color temperature (wavelength distribution).
The endoscope apparatus of the second embodiment presents images
that faithfully reflect the color of a lesion in the body cavity of
a subject or an internal structure of a piping when actually
observed therethrough. Thus, for instance, the lesion in the body
cavity of the subject is easily and properly diagnosed.
The gain setting circuit 71, the selector 72, and the A/D
converters 73 and 74 are arranged corresponding to the light
sources 3A and 3B in this embodiment. Alternatively, however,
instead of these units, a programming tool may be connected to the
serial terminal 18 to rewrite an operation program in the DSP
controlling computer 36 to perform a similar job.
The white balance is set in accordance with the wavelength
distributions of the light emitting lamps of the light sources 3A
and 3B in this embodiment. The white balance is set in
consideration of variations in the color separation filter of the
CCD 26 and transmission characteristics dependent on the wavelength
of the light guide 15.
Referring to FIG. 8, for instance, the R gain and B gain determined
by the gain setting potentiometers 75r and 76r are set to be in the
white balance state (with a white object picked up as a reference)
when the light source device 3A or 3B is connected to the endoscope
2I. In this arrangement, the white balance is set in consideration
of the characteristics of the light guide 15 and the CCD 26 in the
endoscope 2I.
In accordance with the present embodiment, the CCU 29 is set to be
compatible with the CCD 26 in the endoscope 2I as in the first
embodiment. When the light guide 15 in the endoscope 2I has
different characteristics or when the light source device connected
to the endoscope 2I is changed, a proper white balance state is
set.
Also as in the first embodiment, the CCU 29 includes the common DSP
board 30 and the function adjustment/expansion circuit board 31,
having a different setting so that the CCU 29 is compatible with
the endoscope 2I even with the insertion length thereof different
at a low cost involved. Furthermore, a proper white balance state
is set regardless of variations, if any, in the color separation
filter and the light guide 15.
Third Embodiment
A third embodiment of the present invention is discussed referring
to FIG. 10 and FIG. 11. FIG. 10 shows the construction of an
endoscope apparatus of the third embodiment of the present
invention with an endoscope 2A incorporated. FIG. 11 is a block
diagram showing the construction of an electrical system of the
endoscope apparatus.
In this embodiment, a motorized flexing mechanism is arranged in
the endoscope 2I in the first embodiment.
An insert section 11A in the endoscope 2A shown in FIG. 10 includes
an end portion 24, a bending portion 82 that is freely bent, and a
flexible portion 83 having flexibility. The bending portion 82 is
constructed of a plurality of barrel segments in a manner such that
adjacent barrel segments 84 are bendably connected to each other in
a cascade using link means such as rivets. The ends of a pair of
angle wires 85u and 85d for bending the bending portion 82 are
connected to the distal barrel segment at positions corresponding
to the upward positions of the angle wires. The proximal ends of
the angle wires 85u and 85d are entrained about a pulley 86a
arranged in the control section 12. The pulley 86a is connected to
an upward and downward bending motor 87a.
Left and right angle wires 85l and 85r (see FIG. 11) arranged on
the left and the right, arranged 90 degrees away from the angle
wires 85u and 85d within the insert section 11A are entrained about
a pulley 86b within the control section 12 and the pulley 86b is
connected a left and right bending motor 87b.
Referring to FIG. 11, the motors 87a and 87b are driven by a motor
driver 88, which is in turn controlled by the DSP controlling
computer 36.
The DSP controlling computer 36 is connected to an upward and
downward bend direction control knob 89a and a left and right bend
direction control knob 89b. By tilting the bend direction control
knobs 89a or 89b, a command signal responsive to the command
direction is input to the DSP controlling computer 36. The DSP
controlling computer 36 outputs, to the motor driver 88, a control
signal responsive to the commanded direction to cause the motor 87a
or 87b to rotate. One of the angle wires 85u, 85d, 85l, and 85r is
thus pulled, and the bending portion 82 is bent toward the angle
wire 85k (k=u, d, l, and r).
With this arrangement, the bending portion 82 can be bent toward a
desired direction with only a light force because of motorized
driving, compared with a manual bending operation in which the
angle wire 85k is pulled by hand.
The bend direction control knobs 89a and 89b are respectively
tilted upward or downward, and leftward or rightward. These knobs
may be replaced with a single joystick which is tilted in any
direction upward or downward and leftward or rightward.
The rotary shafts of the motors 87a and 87b are respectively
provided with encoders 91a and 91b to detect the amount of rotation
of the motors 87a and 87b. The detected amount of rotation is input
to the DSP controlling computer 36. Based on the detected amount of
rotation, the DSP controlling computer 36 determines whether a
commanded bend is achieved.
When the encoders 91a and 91b detect a maximum bend in each bend
direction, the DSP controlling computer 36 stops the rotation of
the motor 87a or 87b.
In this embodiment, a PAN function (scanning upward and downward)
and a TILT function (scanning laterally) of a digital ZOOM
processor 47c arranged in the DSP 32 for enlarging the image
through signal processing are controlled in this way.
To this end, a control switch unit 90 is arranged. The DSP
controlling computer 36 receives command signals from switches 90u,
90d, 90l, and 90r arranged in corresponding positions thereof in
the control switch unit 90 when these switches are operated. An
observed image is moved in a commanded direction and a function
similar to the bending operation is thus performed.
Furthermore in this embodiment, a selection switch 93 is provided
to switch between the angling operation by the bending operation
knobs 89a and 89b, and the PAN and TILT operation.
For instance, when a maximum bend is achieved in the angling
operation by the bending operation knobs 89a and 89b, followed by
the angling operation function by the selection switch 93, and then
the bending operation knobs 89a and 89b are operated in excess of
the maximum bend angle, the PAN and TILT operations are controlled
in the zoom operation so that the image is observed in excess of
the maximum bending angle.
In this embodiment, the bending operation knobs 89a and 89b, and
the control switch unit 90 are arranged on the control section 12
as shown in FIG. 10.
Furthermore in this embodiment, an unshown neutral switch is
arranged to revert to a neutral position when the PAN and TILT
operations are carried out in the zoom process.
Referring to FIG. 10, power is supplied from a power supply
terminal 94 of the light source device 3 to the DSP board 30 and
the function adjustment/expansion circuit board 31 (simply referred
to as expansion board in FIG. 10) in the CCU 29 through a power
supply line 95.
A main power switch 96 is arranged on the control section 12. FIG.
10 and FIG. 11 show the construction of the endoscope 2A, and the
other endoscopes 2B and 2C also have the same construction. The
remaining construction of this embodiment remains unchanged from
that of the first embodiment.
In this embodiment, by operating the bend direction control knobs
89a and 89b, the bending portion 82 is bent toward a desired
direction.
The operation of the control switch unit 90 permits observation in
a direction beyond the maximum bend angle by the bend direction
control knobs 89a and 89b. Ease of use is assured by the operation
of the selection switch 93 so that observation is permitted in a
direction beyond the maximum bend angle by the operation of the
bend direction control knobs 89a and 89b only.
In this case, if the selection switch 93 is set to the PAN and TILT
operation side, the bend direction control knobs 89a and 89b alone
perform the PAN and TILT function.
The bending of the bending portion 82 is performed as follows.
When one of the bend direction control knobs 89a and 89b is moved,
the DSP controlling computer 36 causes the motor 87a or 87b to
rotate, thereby commanding the angling operation to operate. When
the motor 87a or 87b rotates until the limit of angling operation,
the motor 87a or 87b stops in response to the output of the encoder
91a or 91b.
Subsequent to the stop of the rotation of the motor 87a or 87b, the
DSP controlling computer 36 sends the PAN and TILT of the digital
ZOOM processor 47c of the DSP 32 to perform the PAN and TILT
operation matching the bending command from the bend direction
control knob 89a or 89b.
If the motorized bending operation and the PAN and TILT operations
are interlocked, the operation of the bend direction control knobs
89a and 89b only permits observation in a direction in excess of
the maximum bend angle, assuring the ease of use.
In a system power OFF operation, the DSP controlling computer 36
puts the motorized angle (of the bending portion 82) to a straight
line state with the CCU 29 continuously outputting the video
output, and then cuts off unshown DC output (power). In this
automatic operation, the insert section 11I is pulled out of the
subject being examined without exerting undue force to the angling
mechanism.
This is the advantage that is achieved by the power source, the CCU
29, and the DSP controlling computer 36 for controlling the
motorized angle under coordinated control.
The angle of the insert section 11I is controlled by an external
personal computer 6 through communications. A sophisticated
automatic angling operation is carried out, using video processing
functions of the external personal computer 6.
Separate control SWs may be used to digitally control PAN and TILT
operations.
Besides the advantages of the first embodiment, in accordance with
the present embodiment, the bending portion 82 is easily bent
toward a desired direction by operating the bend direction control
knobs 89a and 89b arranged on the control section 12.
By operating the control switch unit 90, observation is permitted
through the PAN and TILT of the digital ZOOM processor 47c.
In accordance with this embodiment, the zoom function (ZOOM, PAN,
and TILT) by the DSP 32, and the motorized angle-related control
are interlocked by the DSP controlling computer 36. Alternatively,
with the selection switch 93 dispensed with, the motorized angle
control by the bend direction control knobs 89a and 89b, and the
PAN and TILT control in the digital zoom process by the control
switch unit 90 may be independently performed.
Fourth Embodiment
A fourth embodiment of the present invention is now discussed,
referring to FIG. 12 through FIG. 14. This embodiment performs the
signal processing compatible with a CCD having different number of
pixels in the third embodiment.
FIG. 12 shows the construction of an endoscope system 1'' of the
fourth embodiment of the present invention. In this embodiment, CCD
26A in an endoscope 2A, CCD 26B in an endoscope 2B, and CCD 26C in
an endoscope 2C are different from each other in the number of
pixels.
The number of pixels in both a horizontal direction and a vertical
direction in the CCDs 26A, 26B, and 26C are related as follows:
(the number of pixels of) CCD 26A>(the number of pixels of) CCD
26B>(the number of pixels of) CCD 26C. In other words, the CCD
26A has a maximum number of pixels.
The endoscope 2A with the CCD 26A having the maximum number of
pixels has the same construction as the one shown in FIG. 11, and
the discussion about it is omitted.
In the DSP board 30 combined with the CCD 26A having the maximum
number of pixels, the crystal oscillator circuit 59 oscillates,
giving a reference clock corresponding to the CCD 26A having the
maximum number of pixels.
In the CCD 26B or CCD 26C having a smaller number of pixels than
that of the CCD 26A, a standard video signal is generated even with
a different number of pixels to output a signal to the
liquid-crystal display monitor 4 by using the function
adjustment/expansion circuit board 311, partly different from the
function adjustment/expansion circuit board 31 in construction.
FIG. 13 shows the electrical system of the endoscope 2B (or 2C)
that employs the CCD 26B (or 26C).
In the endoscope 2B shown in FIG. 1.3, a digital luminance signal Y
and digital color signals C (color-difference signals U and V)
output by a digital input and output controller 47a in the DSP 32
in the DSP board 30 of the endoscope 2A shown in FIG. 11 are
temporarily stored in a frame memory 97 in the function
adjustment/expansion circuit board 31'', then read from the frame
memory 97 with a standard video period, and converted into an
analog luminance signal Y and analog color signals C by a D/A
converter 98. The analog luminance signal Y and analog color
signals C are then converted by and RGB encoder 99 into an RGB
signal, which is then output through a video output terminal
16.
The frame memory 97 has a memory capacity accommodating the CCD 26A
having the maximum number of pixels (although the CCD 26B is also
acceptable, the CCD 26A is used here so that the arrangement of
this embodiment may be also used in the next embodiment).
The digital input and output controller 47a operates to output the
digital luminance signal Y and digital color signals C
corresponding to the number of pixels of the CCD 26A. When the CCD
26B (or CCD 26C) having the smaller number of pixels is used, the
digital input and output controller 47a outputs a signal (a dummy
signal) having no signal portion that is read from a portion beyond
the pixels of the CCD 26B. The frame memory 97 stores the dummy
signal for the portion beyond the number of pixels of the CCD 26B
along with the signals for the pixels of the CCD 26B.
In other words, the frame memory 97 stores the dummy pixels in some
of memory cells in the horizontal and vertical directions when the
CCD 26B (or 26C) is used. When the signals are read therefrom, only
the signals for the pixels are read under the control of the DSP
controlling computer 36. The read digital luminance signal Y and
color signals C are then converted by the D/A converter 98 into the
analog luminance signal Y and analog color signals C, which are
then converted into an RGB signal by the RGB encoder 99. The RGB
signal is output through the video output terminal 16.
The display area thereof changes, depending on the number of pixels
of the CCD 26I, in the liquid-crystal display monitor 4.
In the CCD 26B and CCD 26C having the smaller numbers of pixels,
the area for the video display might become smaller. However, the
digital ZOOM processor 47c in the DSP 32 varies the zoom
magnification thereof to provide enlarged output to a TELE side.
The size of the display area is substantially constant regardless
of the number of pixels for the CCD. In this way, a video is
presented on a full display screen regardless of the number of the
pixels of the CCD.
In the CCD of a typical interline transfer standard TV signal (NTSC
or PAL, for example), the number of pixels in the horizontal
direction varies according to the number of pixels of the CCD, and
the horizontal resolution thereof varies. Specifically, the larger
the number of the pixels, the higher the resolution of the monitor.
In the vertical direction, however, the number of pixels remains
constant regardless of the changing number of pixels, and the
vertical resolution remains constant regardless of the changing
number of pixels. This is because the TV standards specify the
constant number of scanning lines in the vertical direction.
If the CCD 26B or CCD 26C, having the smaller number of pixels, is
driven by the DSP board 30, a vertically extending image with the
horizontal size thereof contracted might be presented. To correct
this, the digital ZOOM processor 47c increases the zoom
magnification thereof in the horizontal direction to output an
enlarged image to the TELE side. The image contracted in the
horizontal direction is then again enlarged in the horizontal
direction back to its original size. A normal display image is thus
presented on a full display screen.
In this example, by varying the zoom magnification in the
horizontal direction, the normal display image is restored
regardless of the number of pixels of the CCD. The zoom
magnification in the vertical direction may be set to be different
from the zoom magnification in the vertical direction. In this
arrangement, a normal display image is presented on a fully display
screen if a CCD having any number of pixels is employed.
The DSP controlling computer 36 may store the zoom magnification
for full display presentation. In this arrangement, the zoom
magnification is transferred to the DSP 32 each time power is on in
the endoscope 2B, and a full display presentation is operative from
power on of the endoscope apparatus.
Besides the advantages of the third embodiment, in accordance with
this embodiment, the same DSP board 30 and the function
adjustment/expansion circuit board with its construction slightly
modified work with the CCD 26I having a different number of
pixels.
Fifth Embodiment
A fifth embodiment of the present invention is now discussed,
referring to FIG. 14. The fifth embodiment is constructed by adding
a freeze function to the fourth embodiment.
In this embodiment, the endoscope 2A employs the function
adjustment/expansion circuit board 31'' as in the other endoscopes
2B and 2C in the fourth embodiment. Specifically, when the number
of pixels is different, the common function adjustment/expansion
circuit board 31'' in the endoscope 2A (the other endoscopes 2B and
2C) shown in FIG. 14 is employed.
In this embodiment, a freeze switch 92 is arranged on the control
section 12. A freeze command signal is fed to the DSP controlling
computer 36 in response to the operation of the freeze switch 92.
The DSP controlling computer 36 inhibits the writing onto the frame
memory 97.
The signal, which was written onto the frame memory 97 immediately
prior to the inhibition, is repeatedly output and a still image is
thus presented on the liquid-crystal display monitor 4. When the
freeze switch 92 is operated after the still image is presented,
the write inhibition is released. A moving image signal is then
output from the frame memory 97.
Besides the advantages of the fourth embodiment, in accordance with
the present embodiment, the same DSP board 30 and the function
adjustment/expansion circuit board with its construction slightly
modified work with the CCD 26I having a different number of pixels,
and a still image is presented.
The fourth embodiment may be provided with the function of
presenting a still image when the endoscope 2B or 2C employing the
frame memory 97 is used.
Although the common DSP board 30 is employed in the fourth and
fifth embodiments even when the number of pixels is employed, the
following arrangement may be contemplated. The crystal oscillator
circuits 59 for feeding the reference clock is arranged for cases
of the different number of pixels, and are switched to feed the
reference clock to the DSP 32. A plurality of bandwidth limiting
LPFs for the D/A converter circuit 51, which are optimized for
characteristics for the plurality of pixel number settings, are
arranged on the DSP board 30, and are switched for use. In this
arrangement, the CCD having any number of pixels is driven at an
optimum drive frequency, and the display area does not change,
permitting a full display image to be presented.
Furthermore, to cope with the different numbers of pixels, a
software modification may be introduced in the DSP controlling
computer 36 in the function adjustment/expansion circuit board 31
and a constant modification may be introduced in the CCD drive
circuit.
An automatic lighting adjustment mechanism may be introduced to
automatically set the average luminance level of a picked signal to
be a target luminance level in the lighting control of the
illumination light of the light source.
Embodiments including a combination of part of the above
embodiments fall within the scope of the present invention.
It is obvious that a variety of embodiments are constituted without
departing from the spirit and scope of the present invention. The
present invention is limited by the appended claims only, and is
not limited by any specific embodiment.
* * * * *